Monilethrix

General Discussion

Monilethrix is a rare inherited disorder characterized by sparse, dry, and/or brittle hair that often breaks before reaching more than a few inches in length. The hair may lack luster, and there may be patchy areas of hair loss (alopecia). Another common symptom may be the appearance of elevated spots (papules) surrounding the hair follicles that may be covered with gray or brown crusts or scales (perifollicular hyperkeratosis). When viewed under a microscope, the hair shaft resembles a string of evenly-spaced beads. In most cases, monilethrix is inherited as an autosomal dominant trait.

Signs & Symptoms

In most cases of monilethrix, the hair is normal at birth; it may then be slowly replaced by abnormal hair during the first few months to two years of life. In some rare cases, the hair may be abnormal at birth (congenital). The hair may be sparse, dry, lusterless, and/or brittle. In addition, the hair is unusually short and breaks off before growing longer than a few inches.

Scalp hair is most frequently affected by monilethrix. The entire scalp or small areas of the scalp may be involved. In some cases, the eyelashes, eyebrows, pubic hair, and/or other body hair may also be affected. In addition, the patchy loss of hair (alopecia) is a common characteristic of this disorder. Progressive hair loss may lead to scattered bald patches or baldness.

In most cases of monilethrix, a skin condition known as perifollicular hyperkeratosis may develop. The condition is characterized by firm dark lesions (papules) covered with gray-brown scales and crusts that appear on the skin, especially the scalp.

The severity and progression of symptoms may vary greatly from case to case. In some cases, individuals with monilethrix may experience remission of the disorder for no apparent reason (spontaneously), most often during puberty or pregnancy. In other cases, the condition may remain the same throughout life or the symptoms may become progressively worse.

Causes

In most cases, monilethrix is inherited as an autosomal genetic trait. Genetic diseases are determined by two genes, one received from the father and one from the mother.

Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child.

Some cases of monilethrix result from defects (mutations) in the hair cortex keratin gene(s) (HB1; KRTHB1 and HB6; KRTHB6) located on the long arm (q) of chromosome 12 (12q13). Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Pairs of human chromosomes are numbered from 1 through 22, and an additional 23rd pair of sex chromosomes which include one X and one Y chromosome in males and two X chromosomes in females. Each chromosome has a short arm designated “p” and a long arm designated “q”. Chromosomes are further sub-divided into many bands that are numbered. For example, “chromosome 12p13” refers to band 13 on the long arm of chromosome 12. The numbered bands specify the location of the thousands of genes that are present on each chromosome.

The physical findings associated with monilethrix may result from abnormalities of the hard keratin of hair and nails.

Affected Populations

Monilethrix affects males and females in equal numbers. The exact number of people affected by this disorder is not known. Monilethrix may be apparent at birth or by the age of two years. In some cases, the symptoms may improve at puberty or during pregnancy; in other cases, the symptoms may remain the same throughout life.

Related Disorders

Symptoms of the following disorders can be similar to those of Monilethrix. Comparisons may be useful for a differential diagnosis:

Alopecia Areata is a rare disorder characterized by the progressive loss of hair. It often begins suddenly with oval or round bald patches appearing on the scalp; however, other areas of hairy skin may also be involved. Gradually, the affected skin becomes white and smooth. The hair may regrow in these areas within weeks; at the same time, additional patches of hair loss may occur elsewhere. In some cases, hair regrowth may occur in one area of the scalp but not in others; in other cases, the loss of hair may be permanent and lead to baldness. In a few rare cases, all body hair may be lost. Cases with onset during childhood tend to be more severe than those with an adult onset. The exact cause of Alopecia Areata is not known. (For more information on this disorder, choose “Alopecia Areata” as your search term in the Rare Disease Database.)

Pseudomonilethrix is an extremely rare disorder characterized by sparse, dry, and brittle hair that breaks easily. The loss of hair (alopecia) is a common finding in children with Pseudomonilethrix. There are structural differences between the hair of individuals with Monilethrix and those with Pseudomonilethrix; such differences can only be seen when the hair is viewed under a microscope. Pseudomonilethrix is thought to be inherited as an autosomal dominant genetic trait.

Trichorrhexis Nodosa is a condition in which an affected individual’s hair breaks and splits easily. This may result in scattered patches of hair loss (alopecia) on the scalp. When viewed under a microscope, the hair shafts appear to be covered with white bumps or swellings. These swellings are sites where the outer layers of the hair shafts have broken and split into strands.

There are many other disorders that may be characterized by abnormal hair development. These disorders, which include Menkes Disease, Netherton Syndrome, and Tay Syndrome, are characterized by other symptoms and physical characteristics in addition to abnormal hair development. These additional abnormalities can be used to distinguish these disorders from Monilethrix. (For more information on these disorders, choose “Menkes,” “Netherton,” or “Tay” as your search terms in the Rare Disease Database.)

Standard Therapies

The diagnosis of monilethrix may be confirmed by a thorough clinical evaluation and microscopic examination of the hair. When viewed under a microscope, the hair resembles a string of evenly-spaced beads.

No specific treatment exists for monilethrix. Spontaneous resolution following puberty has occurred in some cases. In affected females, the condition improves during pregnancy. Genetic counseling will be of benefit for affected individuals and their families. Other treatment is symptomatic and supportive.

Investigational Therapies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.

For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov

For information about clinical trials sponsored by private sources, contact:

Years Published

1996, 1998, 2004

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